grey image color restoration after image subtraction

After my image subtraction with Matlab, the subtracted image has some black area formed due to the subtraction. Is there any ways that I can restore the black region to its original color?

I have tried to adjust the brightness or intensity but they did not work.

Answer 1

[Image Analyst]

Are your images color or grayscale?

To avoid clipping to 0, like will happen if you subtract a larger uint8 number from a smaller one, you can cast to double

subtractionImage = double(testImage) - double(backgroundImage);
imshow(subtractionImage, []);

Why are you getting 0? Is it because your test image is the same intensity as your background image there? Or your background image is brighter than your test image?

Why are you doing subtraction? Is it to flatten the background to correct for lighting non-uniformities and lens shading? If so you're probably better off doing a background division rather than a background subtraction.

Can you upload your test image and background image?

[Image Analyst]

@Yiu On LEUNG, are you still there?

[Yiu On LEUNG]

Thank you for the reply. After carefully considering your advices, I realised that it maybe caused by the contrast problem, so I performed some image prepoecessing and solved the issue.

Answer 2

[Walter Roberson]

mask = repmat(all(Subtracted == 0, 3), 1, 1, 3);
Subtracted(mask) = Original(mask);